A review of 36 studies in 16 countries found that a careful
diet and exercising helped reduce excessive weight gain in
pregnancy and enabled more women to deliver naturally.
Around one in four births in the UK are by caesarean which, although
regarded as very safe, can carry a risk of complications.
These include the risk of infections to new mothers, excessive
bleeding and potential damage to surrounding organs.
Risks to the baby include breathing problems, which are fairly
common and mostly affect babies born before 39 weeks gestation.
This usually improves within a few days.
Of the studies in the new analysis, 23 included women of any
weight at the start of the study, seven included obese women
only and six were targeted at overweight and obese women.
The researchers, writing in the British Medical Journal (BMJ),
found that women of any weight offered tailored diet and
exercise advice during pregnancy were less likely to need a
caesarean or gain excessive weight.
There was also some evidence that they were less likely to
develop diabetes in pregnancy.
The advice on dieting included restricting sugary drinks,
switching to low-fat dairy and eating more fruit and veg.
Exercise programmes included aerobic classes and cycling in the
gym, and some weight-based training.
The results showed that dieting combined with physical activity
significantly reduced the mother’s weight gain during pregnancy
by an average of 0.7kg compared with the control group.
The study was led by experts at Queen Mary University of London
(QMUL) using data from more than 12,000 women.
One of the authors, Professor Shakila Thangaratinam, said: “Our
findings are important because it is often thought that
pregnant women shouldn’t exercise because it may harm the baby.
“But we show that the babies are not affected by physical
activity or dieting, and that there are additional benefits
including a reduction in maternal weight gain, diabetes in
pregnancy, and the risk of requiring a caesarean section.
“This should be part of routine advice in pregnancy, given by
practitioners as well as midwives.”
Prof Thangaratinam said that for every 40 mothers who follow a
healthy diet and moderately exercise, there will be one fewer
having a caesarean section.
Changes in lifestyle also reduced the risk of diabetes in
pregnancy by 24%.
At present in the UK, only obese women are offered access to a
dietitian and specific classes for advice on diet and
But Prof Thangaratinam said: “Often with interventions like
these, certain groups benefit more than others, but we’ve shown
that diet and physical activity has a beneficial effect across
all groups, irrespective of your body mass index (BMI), age or
ethnicity, so these interventions have the potential to benefit
a huge number of people.”
The results of the study were recently used by the Department
of Health, which recommends at least 150 minutes of moderate
intensity activity every week.
Royal College of Obstetricians and Gynaecologists spokeswoman
Dr Virginia Beckett said the study adds to existing evidence
that overweight women are at greater risk of pregnancy and
“Overweight women are also more likely to develop health
conditions such as gestational diabetes, high blood pressure
and pre-eclampsia, and blood clots.
“In addition, obesity during pregnancy has been linked to an
increased risk of miscarriage, stillbirth, neonatal death,
premature babies and severe bleeding after birth.
“While most women should put on weight during pregnancy,
consuming too many calories can be detrimental to the mother